Commutator-motor.



C. W. FORNANDER.

GOMMUTATOR MOTOR.

APPLICATION FILED AUG. 26, 1911.

Patented Apr. 15, 19B.

IFE-

g EL3 fahr ENVENTOR WITNESSESI 25 tator bars and to increase the numberof bars. Owing to these changes 1n structure,'

UNITED sTATEs PATENT oEEicE.

CARI; FORNANDER, F WILKINSBURG, PENNSYLVANIA.-

COMMUTATOR-MOTOR.

Specication of Letters Patent.

Patented p 15, 1913.

Application nea august 2e, 1911. serial No. 646,243.

To all whom it'may concern':

Be it known that I, CARL W. FORNANDER,

residing at Wilkinsburv, in the county of Allegheny and State ofennsylvania, a sub-v ject of the King of Sweden, have invented ordiscovered certain new and useful Imrovements in Commutator-Motors, ofwhich lmprovements the following is a specification.

and armature for a commutator motor, particularly a single phasecommutator motor.

For various reasons, well known to those skilled in the art of electricmotor construc` tion and operation, carbon' brushes have very largelydisplaced those made of metal, and this use of carbon in place of metalfor motor brushes` has (owing to the relatively high resistance ofcarbon) necessitated a material increase in the size of the brushes.

Another feature of the modern construction of electric commutator motorsis that it has' 4 been found advantageous to decrease the thickness ofinsulation between the communamelythe' increase in the size of thebrushes and the decrease in the size of commutator bars and theirinsulation', thebrush of a mo- .tor usually extends over twoor morecommutator bars simultaneously, and thereby completes a short circuit,so that what is termed a circulating-current plows around whateverarmature coils the brush bridges.

" To reduce such circulating currents,res1st ences have been placedbetween the commutator bars and the armature coils; but, in so much asthese resistances cut downr the normal opera-ting current as well asthecirculating-current, they are objectionable. The usefulness ofsuch-.resistances however, is

not always limited to that of. ecreasing the .circulating-current, forsuch resistances are useful in starting sometypes of motors, as forexamples. motor designed to be'operated by an a-lternatingsingle-phasecurrent.

The object of my invention is to construct a brush composed 'ofdesiredhi material,.such as carbon,and aving such i structural relation tothelcommutator bars and their insulation that the'- resistances,

l heretofore spoken of, may be'pl'aced outside of the armature andwithin control 'of the 55, operator.

My invention relates to electric motors and l has to do with theconstruction of a brush 'multiple wind' l1 resistance My inventionl isillustrated 4in the accompanying drawing, which'forrns Vpart of the'specicatiom and in which- Figure 1 is a diagrammatic representation lofan armature 'and brush; Fig. 2 .a view used to designate like parts.

In the practice of my invention I employ a laminated brush, that is, abrush composed of alternate lalyers o'f conducting and insulatingmateria and I proportion the parts of the armature and brush in suchmanner as t eliminate all circulating-currents of the armature coilsunder the brush. To proportion the parts that such ai end may beaccomplished, five things are taken into' conf sideration, thearmature-winding, the 'thick-'V nesses of commutator bars,commutatorrbar insulations, brush laminae (and bylsuch lis meantthelayers of. conducting material used in the construction of thebrush), and* l' .brushinsulations (by which is meant the layers ofinsulation between the brush lam-4 inre). 'Of these several elementssomeare chosen, to best meet the practical construction of the motor andothersare determined,

preferably by mathematical deductions, such .as will hereinafter bedescribed. Referring to the drawing, wherethesc elements are cated byCB, the commutator-bar insulations byl CI, the brush lamn by BL, the

brush insulations by BI, and the,L armature winding by A', A* 'and A.

diagrammatically shown-intheir relation to l' each other, the commutatorbars are'indi Instead of using a single closed-circuit' -nectingconsecutively each commutator bar with the winding, I preferably windthe armature in such a way that adjacent bars are of the armature,andconnot electrically connected by the'interven-j- 7 ing armaturewinding. 'I his end maybe accomplished in several ways.

First, a4 sin-- gle winding maybe used and connected to alternatecommutator bars, leaving the inthree: independent windings, A,'A2 andA3,

each being connected to ever;7 third commutator bar, a'nd it will beunderstood that any number ofy independent windings may be used V in thesame way as is illust-rated for the double and triple windings. For eachof -these several forms of winding, 1 pro- 'vide a brush,l which (asheretofore stated) will eliminate the undesirable circulatingcurrentsbeneath the brushes. While 1 do not Wish to limit, to. any one speclficapplil cation, my method of proportioning the thicknesses of the brushlaminac, commutator bars -and insulations for each, for the sake ofillustration I prefer to describe-my invention in its relation to asingle-phase commutator motor wound in such a way as to 'havedjacentcommutator bars unconnected, suchas is' shown. in Fig. 1. And inso much as -it is advantageousowing -to the resist--4 ance'of carbon orcompositions ofsimilar vlelectrical "qualities, to. have the lamina@ asthick as possibleI will describe my inventionv'also using such lamina'e.

Referring to Fi 4 and 5, the commutat'or bars CB1, B1, CBS, etc., ofequal thickness are shown lying-in a plane 3 etc.,'which are also ofequal thickness.- Ad- 'acent to the lower side 'of the commutator arsand-insulations a brush is shown consisting of lamin of carbon BL1,'BL1,and BL having equal thickness and separated by equal thicknessinsulations B11 and B12. 1n

. the 'operation of the motor the commutatorbars rotate with Vthearmature. while the brushes 'remain practically stationary, the

. surface of division between the two being indicated by the line 2. 4When'the brush-laminare are of less thickness than the commutator bars,but of a maximum thickness subject to the condition commutator bar CB1having but one -brush lamina B111 in contact with it. 1t will` readilyyb e seen that, when the brush lamina BL2 is thinner than the'commutatorbar CB2, in rorderto prevent a circulating-current flowing, as indicatedby the dotted line 3, through the several conductors CB1, B111, CB2,B13, CBS, and .A2, the brush insulations B11 and BPmust touch orover-lap the commutator insulations C11 and C12 respectively. Thelimiting arrangement will be when 'the' outer edges of the brush insula-'tions B11 and B12 just touch the inner ed es v of the commutatorinsulations C11 and C12 respectively, so that the first vcondition of,preventin i circulating-currents beneath the 80 brush wil be met if theparti. 'are so pro- 'portioned that the thickness of two brushfinsulations plus that of one brush lamina @equals the thickness of onecommutator bar. 'Such relation may be expressed by the equation (A)QBBIJFBLcB .wherein theseveral terms express the thicklnesses ofthe-parts represented by the'm. 'The second condition is thatcirculating-curi' rents must be prevented through the arma"-fture:.windingfconnecting alternate comm'u# tnior bars, lwhen twobrushlam'inae are in bar. Thiscondition is illustrated in Fig.` 5, in amanner similar to the illustration". ,(in Fig. 4) of the firstcondition. l1t will readily be seen that, whenf'the"brushflami-` .-laeare of maximum thickness subject to the laore-s'tated conditions of thisspecific illus-1 tration, the'li'miting arrangement to reventcirculating-currents (as indicated y the dotted line 3%) through the4several condoctors CB1, BL1, CB2, BL2, CBa and A1, will be when theinterior` edges-of the brush insulations B13 and B12 just touch theexterior edges of the commutator insulations C11 and C1112 p ectively.Therefore, the ,second condition will be met if the parts are soproportioned that the thickness ofV one brush insulation plus that oftwo'brushlaminae is equal to the thickness of one commutator bar plusthat of two commutator insulations. This relation may also be eX-pressed by an equation, such equation beiig.

.-vherein the several terms express thel thicknesses of the parts theyrepresent.

The equations thus formulated areA algebraically independent equationsand maybe used as desired to determine one or two unknown quantities.For example, in designing and proportioning the parts in accordance withmy invention the thickness of the commutator bars and the thickness ofthe commutator insulations may be chosen, and, vfrom 'the two equations,the thicknesses of the brush laminac and the brush insulationscm'etactwith the intervening"comnnc'ator'" may be computed. When such aproceeding is followed and they commutator -bars are accurately `spaced4on the armature, a ma-Ximum thickness of brush laminas will beobtained. However, to have greater insurance againstcirculating-currents (in case the coinniutator bars' are not accuratelylspaced) the brush insulations i may be slightly thicker than therequired thickness, (providing the brush laminae are madecorrespondingly thinner). By like procedures similar equations may beformulated for armature windings wherein every third, fourth, etc.,comniutator bar is connected in series' winding. And I have found suchequations, when brush laminae thinner than the commutator bars arechosen, bear a certain fixed relation to'those formulated for acommutator, wherein alternate bars are connected in series. Under allconditions of winding equation (A) remains the same, while equation (B)changes for each winding, the change consisting of adding to each termof the equation the thickness of one part (represented by that term) foreach additional winding to the one wherein alternate bars are connectedin series. For example, when three armature windings are used, asillustrated in Fig. 2, equation (B) becomes 2CB+8CI=3BL+2BI l (suchbeing illustrated in Fig. 3) and when four armature windings are used,equation (B) becomes 3CB+4GI24BL+3BL etc.,

it being observed that the thickness of one part, represented by eachterm, is added to that term for each winding. Equation B may be madegeneral for any number of armature windings by letting X represent thenumber of windings. When thus expressed equation B becomes By properlyusing these equations in conjunction with equation (A) the thickness ofthe desired parts may be obtained, as has been explained heretofore, for:ny desired armature winding.

It will be understood of my invention,

- thus far explained, that any desired 'number of brush laminae may belused, providing they are of the required thickness and spaced evenlywith th proper thickness of insulations.

In the construction of my laminated brush, each lamina may beelectrically connected to the feed wire in such a manner as tov reduceto a minimum the circulatingcurrent, which, in some forms of motors, m.y be established from one brush lamina to another through their exteriorconnections to the feed wire. In Figs. 1 and 2 the meansfor cutting downsuch exterior cirdivided into three conductors each of which` isconnected to a lamina of the brush through an interposed olimicresistance R. A similar construction is shown in Fig. 2, wherein theline wire L divides into four arts, each leadingto a lamina through aninterposed resistance R. i

An alternate means forl reducing the eX- terior circulating-current isillustrated in Fig. 6 and is adapted to be used with `or without theohmic resistance. This altei'- nate means consists of an iron core 4upon which the divided feed wire L is divided and wound in the form of acoil. Ilie feed wire will preferably be so located as to have equalportions of the coil on each side of its connection to it; the resultbeing that, owing to the transformer action, the feed or main linecurrent will not be reduced, while, at the same time, the circulatingcurrents are reduced. Ohmic resistances R may also be placed in each ofthe divided sections of the' feed line, as is shown in the drawing.

In Fig. 3 I have shown, in section, a brush constructed according to myinvention and placed in operative'relation to a series of commutatorbars. The brush-laminas BL are of the proper thickness (relative to thecommutatoi bars and insulations) to prevent circulating-currents beingestablished under thebrush. These laminze are suitably separated byinsulations BI of the proper able. Also in the practice of my invention,

all circulating currents through the armature windings beneath thebrushes are eliminated.

Other important vglidvantages of my invention readily suggest themselvesto those skilled in the art.

I claim herein as my invention.:

In an electric motor, the combination of an armature having a commutatorconsisting of bars of equal thickness separated by insulation bodies ofequal thickness, said armature Wound with a plurality of closed circuitmultiple windings each electrically connected to an equally spacedseries of commutator bars, and a brush consisting of a plurality ofconductin laminas of equal thickness spaced equal distances apart; thethicknesses ofthe bars and the insulation laminas of said coinmutator,the thicknesses commutator, and4 X the number of said armature windings,the said several dimensions being taken circumferentially in thecontact.v surfaceof said commutator, stantially as described.

In testimony whereof I have hereunto set my hand.

Witnesses:

v PAUL' N'. CRI'rcHLow, G, G. TRILL.

' CARL w. FORNANDER.'

